Simulation of a radiological accident involving a radioisotope thermoelectric generator

Radioisotope Thermoelectric Generators (RTGs) are devices that convert heat from radioactive decay into electrical energy and are used in remote locations due to their low maintenance requirements. Various types of RTGs were produced with sources containing large amounts of Strontium-90, which require multiple layers of shielding materials. However, the lack of control and the ease of access to the source increase the biological risk in the event of a breach of the device. Using Monte Carlo simulations, the doses received by an individual involved in an accident were analyzed - first with the device intact, and subsequently with the source exposed due to a breach, such as the one that occurred in Lia, Georgia. The modeling scenario was created in Blender software, employing a BETA-M type generator and anthropomorphic virtual mesh phantoms. The results showed that with the device fully sealed, the effective dose rate was approximately 0.03 mSv/s, whereas in a scenario with the shielding removed and the source placed 30 cm from the thoracic region, this rate reached 7.33 mSv/s. In a face-level exposure situation, the dose to the eyes reached 85.2 mSv/s, exceeding the annual occupational limit in just 3 s. The isodose profile at 20 cm from the source showed that the radiation flux at a 7.5 cm radius was about five times higher than at 15 cm. These results provided insight into the doses received by the individuals in the Lia accident, highlighting the risks associated with such devices.